Document EP 2226277 B1 describes a rotary conveyor for transferring containers comprising a rotor operated by a motor for rotating about a rotation axis. The rotor has a perimetric wall with a plurality of suction openings distributed along its periphery in correspondence with retaining elements configured for being coupled with the containers. In an inner region of the perimetric wall of the rotor, there is a stationary suction chamber connected to a low pressure source. The suction chamber defines a laterally open channel facing the perimetric wall along a predetermined circumferential arc, such that the suction chamber is partly demarcated by the perimetric wall of the rotor and such that when the rotor rotates, the suction openings are communicated directly with the suction chamber along the predetermined circumferential arc. As the rotor rotates, a container is retained in each of the retaining elements by suction at the start of the predetermined circumferential arc, conveyed by the rotor along the predetermined circumferential arc, and released at the end of the predetermined circumferential arc.
Document EP 2722296 A1 discloses a rotary conveyor with suction and change of pitch for transferring containers, comprising a rotary platform rotating about a rotation axis, a plurality of guiding elements fixed to the rotary platform and a plurality of grooves parallel to the guiding elements formed in the rotary platform. The guiding elements and grooves are uniformly distributed around the rotation axis and extend from a peripheral region to a central region of the rotary platform. A stationary closed-loop cam defining a path not centered with respect to the rotation axis is located below the rotary platform. Each guiding element has coupled thereto a runner provided with a cam follower inserted through the corresponding groove and coupled to the closed-loop cam, such that each runner performs a back and forth movement along the corresponding guiding element during one rotation of the rotary platform.
In the rotary conveyor of the mentioned document, EP2722296A1, each runner has fixed thereto a retaining element provided with a suction port suitable for retaining a container, and each suction port is in communication with a suction chamber through a corresponding suction conduit. The suction chamber is located in a stationary position below the rotary platform and has an upper wall in contact with a lower surface of the rotary platform. The closed-loop cam and a suction groove parallel to a portion of the path defined by the closed-loop cam are formed in this upper wall of the suction chamber. The suction conduit of each runner has an open lower end which communicates with the suction chamber through an intersection of the corresponding groove formed in the rotary platform and the suction groove formed in the suction chamber, and this open lower end of the suction conduit follows the changing position of the mentioned intersection during the back and forth movement of the runner occurring during a part of each rotation of the rotary platform.
The rotary conveyor of the mentioned document EP2722296A1 has several drawbacks. First, the fact that the upper wall of the suction chamber is in contact with a lower surface of the rotary platform can generate considerable friction resulting in unacceptable component wear and/or heating. Furthermore, the fact that both the closed-loop cam and the suction groove are formed in the upper wall of the suction chamber makes it necessary to replace the entire suction chamber when only the path of the closed-loop cam is to be modified. On the other hand, using grooves formed in the rotary platform both for the passage of the corresponding cam followers and for the passage of air at their intersections with the suction groove requires high precision in the paths of the closed-loop cam, the grooves formed in the rotary platform and the suction groove for obtaining an acceptable air flow rate in any position without considerable losses, which imposes certain limitations in the design of such paths.